P-type zinc oxide spinels: application to transparent conductors and spintronics

Abstract

We report on the electronic and optical properties of two theoretically predicted stable spinel compounds of the form ZnB 2 O 4 , where B = Ni or Cu; neither compound has been previously synthesized, so we compare them to the previously studied p-type ZnCo 2 O 4 spinel. These new materials exhibit spin polarization, which is useful for spintronics applications, and broad conductivity maxima near the valence band edge that indicate good p-type dopability. We show that 3d electrons on the octahedrally coordinated Zn atom fall deep within the valence band and do not contribute significantly to the electronic structure near the band edge of the material, while the O 2p and tetrahedrally coordinated B 3d electrons hybridize broadly in the shallow valence states, resulting in increasing curvature (i.e., decreased electron effective mass) of valence bands near the band edge. In particular, ZnCu 2 O 4 exhibits high electrical conductivities in the p-doping region near the valence band edge that, at σ = × − 2 10 S cm 4 1 , are twice the maximum found for ZnCo 2 O 4 , a previously synthesized compound in this class of materials. This material also exhibits ferromagnetism in all of its most stable structures, which makes it a good candidate for further study as a dilute magnetic semiconductor.

p-Type Ultrawide-Band-Gap Spinel ZnGa2O4: New Perspectives for Energy Electronics

“…According to the first-principles calculations based on the density functional theory of Chao et al [57] , with the introduction of the Zn impurity (Ga substitutional), the Zn atom loses almost all valence electrons (since the Zn electronegativity is lower than Ga and the Zn 2+ valence electrons are less than Ga 3+ ) which may explain the Zn2p shift towards larger binding energies with increasing Zn-flux. donor and VGa as acceptor) and interstitials, dominant defects in spinels are suggested to be antisites [18] .…”

“…In particular, some very recent works such as the ones from Hrong et al [1] and Galazka et al [16] have evidenced the great prospects of n-type ZnGa2O4 as potential semiconductor platform for future ultra-wide bandgap oxide optoelectronics [17] . In this work, we show that engineered ZnGa2O4 epitaxial single crystal layers may also be an ultra wide bandgap native p-type semiconductor with great dopability prospects owing to the spinel's inherent diversity of choices of cation coordination [18][19] . Spinels generally refer to compounds with formulation AB2X4 where A 2+ is a divalent cation such as Zn, Ni, Cu, Sn, Mg, Cr, Mn, Fe, Co or Cd, B 3+ is a trivalent cation such as Ga, Al, In, Ti, V, Fe, Co, Ni, V, Cr, Mn and X 2is a divalent anion such as O, S or Se [20] .…”

Investigation of self-consistent site-dependent DFT + U effect on electronic band structure and optical properties of SiFe2O4 spinel

“…Spinel-type transition-metal oxides encompass a group of compounds having a general chemical formula of XM 2 O 4 , with M and X cations occupying two nonequivalent lattice sites: one with six octahedrally (O h ) coordinated oxygens and the other with four tetrahedrally (T d ) coordinated nearest-neighbor oxygen atoms [6].…”

Machine Learning Optimization of p-Type Transparent Conducting Films

“…[1][2][3][4] Oxides such as delafossites (e.g., CuAlO2, CuGaO2, CuInO2, etc.) 5 , spinels (AB2O4, e.g., NiCo2O4) 6,7 , and mixed oxides (e.g., In2O3-Ag2O) 8 have been investigated as p-TCMs in the past few years, 9 but it has been difficult to obtain the desired combination of high transparency and conductivity. Sulfides have also been investigated as TCMs.…”